Biogas is considered as an excellent fuel because: (i) It causes no pollution, as it is environmental friendly. (ii) Biogas plant from which biogas is produced serves as an excellent way of waste disposal. (iii) It is economical and produces a large amount of heat per unit mass.
Modern periodic law states that the physical and chemical properties of an element are the periodic function of the atomic number of that element. Electronic configuration of the elements play an important role in the placement of elements in the modem periodic table. The valence shell electron of an element decides its position in a particular group or period for example: if the configuration of an element is 2, 1 it means that the Li = 2, 1 It belongs to the 2nd period and 1st group.
The ability of the eye lens to adjust its focal length is called the power of accommodation. There should be a contraction . of ciliary muscles, that will increase the curvature of the eye lens and becomes thicker, so the focal length of the eye lens will decrease. It will thus enable us to see the objects clearly.
2AgCl → 2 Ag + Cl₂ Initially, the colour of silver chloride is white but when it is kept in sunlight it breaks down to give silver and chlorine. Hence, the colour changes to grey. It is an example of Photo-Chemical Decomposition reaction.
NaCl is made by reacting an acid and a base. The base is NaOH (Sodium hydroxide). So, HCl + NaOH → NaCl + H2O It is a Neutralization Reaction. It is known as rock salt in crystalline form. It is the result of the evaporation of ancient oceans millions of years ago. Sometimes pressure from deep inside the Earth forces up large masses of rocks to form salt-like domes.